/**
 * 529. 扫雷游戏
 * https://leetcode.cn/problems/minesweeper/description/
 */
class Solution {
    int m, n;
    int[] dx = {0, 0, -1, 1, -1, -1, 1, 1};
    int[] dy = {-1, 1, 0, 0, -1, 1, -1, 1};
    public char[][] updateBoard(char[][] board, int[] click) {
        m = board.length; n = board[0].length;
        int x = click[0], y = click[1];
        if(board[x][y] == 'M') {
            board[x][y] = 'X';
            return board;
        }
        dfs(board, x, y);
        return board;
    }
    public void dfs(char[][] board, int i, int j) {
        //先统计周围有多少个地雷
        int count = 0;
        for(int k = 0; k < 8; k++) {
            int x = i + dx[k], y = j + dy[k];
            if(x >= 0 && x < m && y >= 0 && y < n && board[x][y] == 'M') {
                count++;
            }
        }
        //判断周围有多少个地雷，0-》B，x-》x
        if(count == 0) {
            board[i][j] = 'B';
            for(int k = 0; k < 8; k++) {
                int x = i + dx[k], y = j + dy[k];
                if(x >= 0 && x < m && y >= 0 && y < n && board[x][y] == 'E') {
                    dfs(board, x, y);
                }
            }
        } else {
            board[i][j] = (char)(count + '0');
            return;
        }
    }
}